Aromatic acid monomers, polymers, products and processes for their manufacture

ABSTRACT

Processes for producing aromatic monomers useful for forming polyesters are disclosed. Cost effective steps employed in the processes permit small amounts of process-related materials typically removed from monomer to remain in an aromatic monomer product. In many cases, the presence of the process-related materials left in the monomer product by the cost effective process steps can enhance the performance of the monomer in certain applications. Aromatic monomer products and polymers produced therefrom having these advantages also are disclosed, as well as products such as pasteurizable bottles made from these polymers

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional PatentApplication No. 60/138,344, entitled “Aromatic Acid Monomers, Polymers,Products and Processes for Their Manufacture”, filed Jun. 9, 1999, andU.S. Provisional Patent Application No. 60/103,393, entitled “AromaticAcid Monomers, Polymers, Products and Processes for Their Manufacture”,filed Oct. 7, 1998.

FIELD OF THE INVENTION

[0002] The invention generally relates to polymers formed from aromaticacids. More particularly, the invention relates to aromatic acidmonomers which contain small amounts of materials that can provideunexpected advantages during the polymerization or copolymerization ofthose acid monomers, as well as to processes for manufacturing sucharomatic acid monomers and polymers.

BACKGROUND OF THE INVENTION

[0003] The manufacture of aromatic acids useful as monomers typically isa complex, multistep process. For example, 2,6-naphthalenedicarboxylicacid (2,6-NDA) can be manufactured by a five step synthesis processwhich includes the steps of reacting o-xylene and butadiene in analkenylation reaction to produce 5-ortho-tolylpentene, cyclizing the5-ortho-tolylpentene to form 1,5-dimethyltetralin (1,5-DMT),dehydrogenating the 1,5-DMT to produce 1,5-dimethylnaphthalene(1,5-DMN), isomerizing the 1,5-DMN to produce 2,6-dimethylnaphthalene(2,6-DMN), and oxidizing the 2,6-DMN to produce 2,6-NDA.

[0004] Crude NDA produced by such a process will contain a wide varietyof what are believed to be undesired process-related materials. Many ofthese materials will be isomers of 2,6-NDA or mono- or trifunctionalreaction products. Other undesired process-related materials containedin the crude NDA will be reagents such as catalyst metals carriedthrough the various reactions steps, and color bodies formed during thereaction steps. As used herein, the term “process-related material”means any material that is formed or added in any process step leadingup to the manufacture of aromatic acid monomer product, including butnot limited to, catalysts, products of side reactions, undesiredoxidation products, undesired isomers and the like.

[0005] It is believed that in the preparation of polyesters frommonomers such as NDA, monomer purity is critical to satisfactorilyachieving high molecular weight polymers and a sufficiently fast kineticrate of polymerization. For this reason, polymer manufacturers typicallyrequire that monomer impurities such as monofunctional and trifunctionalglycols and carboxylic acids be minimized or eliminated from monomers tobe used in polymerization reactions. For example, terephthalic acid andisophthalic acid typically are expected to contain less than 200 partsper million or less by weight total of monocarboxylic and tricarboxylicacids. Similarly, ethylene glycol used in polymerization reactionstypically is expected to contain no detectable impurities.

[0006] Tricarboxylic acids are thought to be undesirable because suchtrifunctional compounds can cause undesired cross-linking of polymerchains. Such cross-linking is reported to contribute to slow rates ofcrystallization and polymer brittleness, both of which are undesiredcharacteristics in many applications. Additionally, when cross-linkingbecomes substantial, a “gel point” is reached. At this point, thepolymer cannot be melt polymerized or melt fabricated and is no longerconsidered to be a thermoplastic material.

[0007] Monocarboxylic acids and other monofunctional materials arebelieved to be undesirable components in monomers because they act as“chain-stoppers” which inhibit the development of molecular weight andbecause they decrease reaction kinetics. If the concentration of suchmaterials is too high, the polymerization rate can become zero due totermination of otherwise reactive end-groups.

[0008] Color bodies of various types are thought to be undesirable inmonomers. The presence of color bodies in monomer can result insubstantially greater color in a polymer than would appear likely fromseemingly small amounts of color visible in a monomer, thus making evenminute amounts of color bodies in monomers undesirable. As used herein,the term “color bodies” refers to any carboxylic acid containingprocess-related material present in a monomer or polymer that cancontribute to the presence of color in the monomer or polymer if presentin sufficient amount.

[0009] Metals such as entrained catalyst metals also are thought to beundesirable components in monomers. For example, entrained cobalt andmanganese oxidation catalyst are believed to be undesirable monomerimpurities because it is expected that they may affect the rate ofpolymerization and polymer color in an unpredictable way. Such metalsalso are thought to sometimes affect the amount of color visible in amonomer or polymer.

[0010] Because it is believed that the presence in monomer of undesiredprocess-related materials such as byproducts, reagents and impuritieslike color bodies can result in an inferior polymer product, substantialeffort typically is devoted to improving the purity of monomers such as2,6 NDA to provide a quality of product deemed acceptable by customers.

[0011] For example, purified aromatic acids have been produced fromcrude aromatic acids by slurrying the effluent from a crude aromaticacid oxidation process, passing the slurry through a plurality ofheaters until the reaction products are dissolved, passing the resultingsolution over a purification catalyst, and thereafter crystallizing apurified product. Such a process requires substantial time and energybeyond that expended to produce crude aromatic acid, and thereforesubstantially increases the cost of the monomer.

[0012] Alternatively, high purity monomer can be manufactured bystarting with a relatively high purity feedstock, such as a process inwhich relatively pure 2,6-naphthalenedicarboxylate (2,6-NDC) ishydrolyzed to form relatively pure NDA. This process also is costintensive because of the complexity and expense of producing therelatively pure NDC feedstock.

[0013] What is needed is a cost effective way to produce aromatic acidssuch as NDA which are suitable for use in polymer applications.

SUMMARY OF THE INVENTION

[0014] Surprisingly, we have found that the presence of certain levelsof process-related materials in aromatic acid monomers can result inmonomers that perform as well as or better than higher purity aromaticacid monomers when used in many polymer applications.

[0015] In some applications, the presence of certain levels of catalystmetals can result in more rapid polycondensation and solid statepolymerization reactions, thereby improving the economics of thesepolymerization reactions without affecting the desired properties of thepolymer product.

[0016] In other applications, the presence of certain trifunctionalmaterials in the aromatic acid monomer product provide for branching ofpolymer chains, thereby providing increased melt strength which isuseful when molding articles from the polymer.

[0017] In still other applications, the presence of certain levels ofmetallic impurities and color bodies provides for an aromatic acidmonomer that has a brownish cast that is useful in particular end uses,including but not limited to the packaging of drinks such as beer inbrown polymer bottles.

[0018] While in some cases the foregoing aromatic acid monomers might beproduced directly as solids separated from the product of an oxidationreaction, typically aromatic monomer product in accordance with thepresent invention will be produced by relatively simple post-processingof oxidized aromatic feedstocks, such as by slurrying or washing crudearomatic acid in an appropriate solvent under the appropriate processconditions. Monomer product manufactured in this way can be both lessexpensive and advantageous in certain end uses.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The following detailed description of preferred embodiments ofour invention focuses on the advantages of our invention with respect tothe preparation of 2,6 naphthalenedicarboxylic acid monomer product andpolymers made therefrom. As will be discussed later in more detail, theadvantages of the invention also are believed to be useful in connectionwith other aromatic acid monomers such as terephthalic acid, isophthalicacid and other isomers of naphthalenedicarboxylic acids.

[0020] As noted above, 2,6-naphthalenedicarboxylic acid (2,6-NDA) can bemanufactured by a five step synthesis process which includes the stepsof reacting o-xylene and butadiene in an alkenylation reaction toproduce 5-ortho-tolylpentene, cyclizing the 5-ortho-tolylpentene to form1,5-dimethyltetralin (1,5-DMT), dehydrogenating the 1,5-DMT to produce1,5-dimethylnaphthalene (1,5-DMN), isomerizing the 1,5-DMN to produce2,6-dimethylnaphthalene (2,6-DMN), and oxidizing the 2,6-DMN to produce2,6-NDA. Aromatic feedstocks such as the 2,6-DMN oxidized in thisprocess preferably contain at least 97 mole percent of the feed materialwhich is to be oxidized to the acid, calculated as a mole percent of allaromatic material in the feedstock.

[0021] Crude 2,6-NDA produced by the foregoing process preferablycontains at least 93 mole percent acid monomer and typically is expectedto contain unacceptable levels of one or more of the followingmaterials: trifunctional materials, 1-bromo-2,6-NDA, 2-naphthoic acid,6-formyl-2-naphthoic acid, cobalt, manganese, bromine, iron and variouscolor bodies. We have found that it frequently is not harmful, and inmany cases it is advantageous, to permit certain levels of metals,trifunctional compounds, and color bodies to be present in 2,6-NDAmonomer product used in polymerization reactions. In many cases, theseacceptable and advantageous material levels can be obtained byrelatively simple processing of the oxidation product of 2,6-DMN,thereby eliminating the need for costly purification steps such asrecrystallization.

[0022] Acceptable and preferred levels of the foregoing materialsconsistent with our invention are listed in Table 1, below. The ppmranges listed refer to ppm by weight of the material present in NDAmonomer product. TABLE 1 Material Acceptable level Preferred Leveltrifunctionals 50 to 10,000 150 to 8,500 monofunctionals 50 to 5,000 150to 3,500 metals (Co + Mn) 50 to 10,000 500 to 2,000 color bodies 50 to500 50 to 250

[0023] NDA monomer having one or more of the foregoing materials inconcentrations in accordance with our invention readily can be produced,for example, by slurrying crude NDA oxidation product to remove afraction of such materials, while permitting a desirable, or at leastnon-deleterious, portion of such materials to remain in the monomer. Asused herein, the term “slurry” refers to any process which employs asolvent to wash or disperse a crude oxidation product, but specificallyexcludes any process which dissolves greater than about 10 mole percentof a desired aromatic monomer present in crude oxidation product, suchas a recrystallization step. Other examples of “slurry” processes inaccordance with the invention include the use of higher solvent volumesin the reactor in which the aromatic feedstock is oxidized to render theprocess-related materials more soluble, thereby somewhat reducing thelevels present in the product, adding or increasing the volume ofsolvent in the crystallizer train of the oxidation process to reduce thepresence of process-related material by dilution, and the use offiltration with a solvent wash to reduce the level of process-relatedmaterials remaining in the monomer product.

[0024] For example, crude 2,6-naphthalenedicarboxylic acid can berecovered directly from 2,6-DMN oxidation mother liquor. The crude2,6-NDA then can be redispersed or reslurried in a suitable solvent suchas water, a low molecular weight carboxylic acid, or a mixture of waterand a low molecular weight carboxylic acid at a weight ratio of about0.1 to about 1 part of 2,6-naphthalene dicarboxylic acid per part ofsolvent. Preferred process conditions for the reslurry process includetemperatures of from 60 to 125° C., with 75 to 110° C. being mostpreferred, and pressures of from about 0.5 to 3 atmospheres, withpressures from 1 to 2 atmospheres being most preferred. Solvent acid towater ratios can range from 100 percent acid to 100 percent water, withthe preferred acid to water part ratio being from about to 90:10 to50:50, with the most preferred ranges being about 80 parts acid and 20parts water.

[0025] Preferably, at least a portion of the solvent used to redisperseor reslurry the 2,6-naphthalene dicarboxylic acid in this manner is aprocess stream or process-derived stream such as condensate from theoverhead of the oxidation reaction mixture. In this case, solventcomprising water and an acid such as acetic acid can be returned, atleast in part, to the oxidation reactor. Alternatively, the solvent canbe distilled to recover the low molecular weight carboxylic acid forrecycle to the oxidation reactor. Solvents may contain other processmaterials that will not substantially affect the slurry process orproperties of the monomer product, such as alcohols or acetatesgenerated in the process. Such process streams should, however, containlittle or none of the process-related materials sought to be minimizedin the slurry process.

[0026] The foregoing slurry step provides for a relatively purer2,6-naphthalenedicarboxylic acid. In many cases, such a 2,6-NDA monomerproduct in accordance with the invention will be suitable or preferredfor certain applications over a monomer product produced from a morecomplex process having additional purification steps.

[0027] After this slurry step, the 2,6-naphthalenedicarboxylic acid canbe separated from the solvent by any method or methods known in the artfor partitioning a solid from a liquid phase such as, for example,centrifugation, filtration, or settling.

[0028] Of particular interest in the reslurried NDA are theconcentrations of catalyst metals such as cobalt and manganese, theratio of cobalt and manganese metals, the level of multifunctionalaromatic compounds, and the level of colored impurities.

[0029] The levels and ratios of catalytic metals are important bothbecause they will affect the polymerization rate of the monomer andbecause their presence may, in some cases, influence the final polymercolor. For NDA applications, the total amount of Co and Mn present inthe reslurried material should be no more than about 10,000 ppm byweight in the reslurried product, with 500 to 2,000 ppm being preferred,and 1000 to 1,500 ppm being most preferred. The molar ratio of Co to Mncan range from 5:1 to 0.2:1, with the preferred ratios being between 4:1to 0.25:1, and the most preferred ratios being between 3:1 and 0.5:1.

[0030] The levels of multifunctional materials are important when thepolymer to be produced from the aromatic monomer requires additionalmelt strength. For NDA applications, trifunctional naphthalenic moietiesare the more likely species, with 1,2,6-, 1,3,7- and 2,3,6-naphthalenetricarboxylic acids predominating in the mix. Preferably, thesetrifunctional species will be present in the reslurried NDA in an amountbetween 50 and about 10,000 ppm by weight, preferably between about 200and 9,000 ppm by weight, and most preferably between about 150 and 8,500ppm by weight. When other aromatic monomers such as PTA are the subjectof the invention, trifunctional acids such as 1,2,3-, 1,2,4- and1,3,5-benzene tricarboxylic acids, and mixtures thereof are the morelikely trifunctional species, and may be present in the ranges set forthabove for the napthalenic trifunctional species. Mixtures of any and allof the foregoing trifunctional impurities may, of course, be present inaccordance with the invention, and impurities having a functionalitygreater than 3 may also be advantageously utilized in accordance withthe invention. As used herein, the term “trifunctional material” meansany process-related material having three functional groups capable ofreacting with a glycol monomer under polymerization conditions. The term“multifunctional material” means any such material with a functionalityof three or more.

[0031] Polyester color is a very important performance requirement incertain applications, while in other applications, color is notimportant. Sometimes, a color such as brown is required for certainpackaging applications. The brown color typically is achieved by theaddition of dyes which usually are high molecular weight organiccompounds. Dyes are undesirable because they can detract from thepolyester properties, especially barrier permeation to gases such asoxygen and carbon dioxide. Additionally, dyes are expensive, and can beundesirable from environmental and recycling standpoints. Thus, colorbodies present in an aromatic acid monomer may be useful for inducing acolor such as brown into subsequently formed polymers. Color bodiesuseful in accordance with the invention include benzcoumarin,pentaquinone, pentacene and flourenone structures containing carboxylicacid functions. Typically, these color bodies should be present in anamount between about 50 and about 500 ppm by weight, more preferablybetween about 50 and 250 ppm, and most preferably present at a level ofabout 150 ppm.

[0032] Slurried NDA in accordance with the invention also can containmonofunctional impurities including, but not limited to, such aromaticacid impurities as benzoic acid and benzoic acid substituted with groupssuch as methyl, bromo, and formyl groups, as well as 1- and 2-naphthoicacid and 1- and 2-naphthoic acid substituted with groups such as methyl,bromo, and formyl, and mixtures thereof. The concentration ofmonocarboxylic acids in a reslurried NDA typically is from about 50 to5,000 ppm by weight, preferably 100 to 4,000 ppm by weight, and mostpreferably about 150 to 3500 ppm by weight. As used herein, the term“monofunctional material” means any process-related material having asingle functional group capable of reacting with a glycol monomer undertypical polymerization conditions.

[0033] Each of the foregoing materials need not be present in theamounts mentioned above if the desired advantage attributable to thatmaterial is not required in the desired monomer application.

[0034] By way of example, the crude NDA can be reslurried to yield anNDA monomer having the approximate specifications set forth in Table 2,below. TABLE 2 Material Level trifunctionals 5,500 +/− 1,500 ppmmonofunctionals 2,000 +/− 1,000 ppm metals (Co + Mn) 1000 +/− 500 ppm color bodies 150 +/− 120 ppm

[0035] Examples 1 and 2, below, demonstrate the effect of cobalt andmanganese metal on the rate of polymerization of an aromatic polymer.The effect of catalytic metals in NDA monomer in a purified terephthalicacid (PTA)/naphthalenedicarboxylic acid (NDA) polymer was demonstratedby comparing the polymerization of an antimony-catalyzed 92 mole percentPTA/8 mole percent NDA mixture polymerized with ethylene glycol (thepolymer being hereafter referred to as “PETN-8”) with that of a similarmixture that had been “spiked” with 90 ppm by weight of cobalt (ascobalt acetate) and 30 ppm by weight of manganese (as manganeseacetate). The polymerization times for both mixtures were measured forpressure esterification, atmospheric esterification and polycondensationreactions.

EXAMPLE 1

[0036] In this example, the melt polymerization of PETN-8 without cobaltand manganese concentrations in the range of the invention wasdemonstrated. The following materials were placed into a 56-liter,helical-agitated reactor: 12.86 kg of ethylene glycol, 27.53 kg ofterephthalic acid, 3.12 kg of 2,6-naphthalene dicarboxylic acid, 1.34grams of tetramethylammonium hydroxide, 8.46 grams of antimony trioxide,and 3.00 grams of cobalt acetate (20 ppm based on polymer yield). Theinitial reactor temperature was 107° C. and the reactor was pressurizedwith 40 psig nitrogen pressure. The melt temperature was increased to223-246° C. and water was removed while the pressure was maintained at40 psig. When water evolution stopped, the pressure was reduced toatmospheric and pressure esterification was completed. The pressureesterification time was 218 minutes.

[0037] The melt temperature then was increased to 263° C. andatmospheric esterification was continued for 60 minutes. An additional100 grams of ethylene glycol and 3.83 grams of phosphoric acid wereadded. The reactor pressure was decreased from atmospheric to 3 mm Hgover a period of 65 minutes as the melt temperature was increased to285° C. Melt polycondensation was continued for an additional 108minutes for a total of 173 minutes of polycondensation time to reach anagitator torque value of 1800 pound-inches. The product was stranded,quenched, and pelletized. The product had an inherent viscosity of 0.58dL/g measured in 60/40 phenol/tetrachloroethane at 30° C. and aconcentration of 0.4 g/dL.

EXAMPLE 2

[0038] The following example demonstrates the melt polymerization ofPETN-8 with cobalt and manganese concentrations present in the range ofthe invention. Example 1 was repeated with the same raw materials andweights except that 4.42 grams (28 ppm based on polyester weight) ofmanganese acetate was added and the amount of cobalt acetate added was13.59 grams (91 ppm based on polyester weight). Using identicaltemperatures and pressures, the pressure esterification time was 220minutes. The atmospheric esterification time was 60 minutes and thepolycondensation time at the 285° C. melt temperature required to obtain1800 pound-inches of torque was 117 minutes. The product's inherentviscosity was 0.59 dL/g.

[0039] As can be seen by comparing Examples 1 and 2, the pressure andatmospheric pressure esterification reactions were completed in about220 and 60 minutes respectively for both the “spiked” and controlsamples of Examples 1 and 2. Beneficially, however, the polycondensationreaction of the “spiked” sample was completed in about 117 minutes, ascompared to about 173 minutes for the control sample. The substantialreduction in reaction time is believed to provide a major economicadvantage in use.

[0040] Example 3, below, demonstrates that the presence of mono- andtricarboxylic acid impurities does not adversely effect the meltpolymerization of PETN-8.

EXAMPLE 3

[0041] Example 1 was repeated with the same raw materials and weights asthe control except that 12.57 grams of trimellitic acid, 3.80 grams of2-formyl-6-naphthoic acid, 2.22 grams of 2-naphthoic acid, and 0.19grams of 2-methyl-6-naphthoic acid were added. High purity NDA obtainedby the hydrolysis of NDC was used in the control, while reslurried crudeNDA obtained directly from an oxidation of DMN was used in the sample inaccordance with the invention. The composition and characteristics ofthe control and the mono- and trifunctional-containing sample are setforth below. Color bodies were present in the crude sample but were notquantified. Impurity (ppm) Control Invention Tricarboxylic Acids None4,029 Monocarboxylic Acids 109 1,993 Catalyst Level (ppm) Cobalt 20 90Manganese None 30 Antimony 200 200 Process Time (Minutes) PressureEsterification 218 215 Atmospheric Esterification 60 60 Polycondensation173 118 Polyester Properties Inherent Viscosity, dL/g 0.58 0.56 Color,*b value −0.38 +14.62

[0042] The reduction in polycondensation time from 173 minutes to 118minutes in accordance with the present invention is believed to be ofmajor economic significance.

[0043] With respect to color, it should be noted that the *b color valuenoted above is a tristimulous color value on the blue/yellow scale. Onthis scale, a negative value appears blue and a positive value appearsyellow, but with *b values greater than about +10, the visual appearanceis brown. Therefore, the polyester prepared according to the inventionparticularly was suitable for beer bottle and other brown containerapplications without the added cost and environmental concern of theaddition of an organic dye or pigment. Such color body-containingpolyesters of this invention also are useful as relatively low costpolyesters in applications where white color is not a requirement, suchas for industrial fibers and insulating films.

[0044] Example 4, below, illustrates the increased ability of polymersin accordance with the invention to polymerize in the solid state.

EXAMPLE 4

[0045] 3.0 gram polymer pellets produced from the materials of Examples1 and 2 were crystallized in an oven at 150° C. for 2.0 hours. Thepellets were placed in test tubes, vacuum was applied, and the testtubes placed in an oil bath at room temperature. The oil was heated overa period of 200 minutes to 410° F. which was considered the startingpoint for solid state polymerization. Samples were periodically removedfrom the oil bath and the following data obtained: Inherent Viscosity(dL/g) Time (Hours) Control Invention Start 0.60 0.58 1.0 0.61 0.62 2.00.62 0.64 4.0 0.65 0.68 6.0 0.71 0.73 8.0 0.75 0.77 Rate (dL/g) 0.01880.0238

[0046] The foregoing data demonstrates an approximately 40 percent solidstate polymerization rate increase for the invention compared to thecontrol.

[0047] Examples 5 and 6, below, demonstrate that films can be formed andstretched from polymers in accordance with the invention, and that thepresence of extraneous material in the polymer does not adversely affectthe film product.

EXAMPLE 5

[0048] Solid state polymerized pellets in accordance with the inventionfrom Example 4 were dried for 16 hours at 150° C. and melt extrudedusing a Killion Model KL-125 single screw extruder equipped with a 1.25inch screw with a length to diameter ratio of 24 to 1 (L/D=24/1). Theextruder was equipped with a six inch adjustable lip sheet die and threechilled temperature rolls for take-off. A heater temperature profile of515/525/530/530/530/500° F. (feed throat to die) was employed and thescrew speed was 75 rpm. High quality, amorphous sheet having a thicknessof approximately 23 mils was produced.

EXAMPLE 6

[0049] Samples of the sheet from Example 6 were biaxially oriented in aT. M Long stretcher. The samples were heated to 226-244° F. for a periodof 2.0 minutes and stretched at a stain rate of approximately300%/second to produce 3×3 biaxially oriented films.

[0050] The following film properties were measured: Property ControlInvention Crystallinity, % 25.0 23.7 Carbon Dioxide Permeation 34.2 31.2(cc-mil/100in2-day-atm @ 35° C.)

[0051] As can be seen from the foregoing data, the PETN-8 copolyestersample of the invention which contained high levels of moncarboxylicacids and tricarboxylic acids exhibited essentially the same level ofcrystallinity as the control sample and both films had similar carbondioxide permeation values. However, the lower permeation value for theinvention translates into longer shelf-life for packaging applications.Both films were very tough and showed no evidence of brittleness.

[0052] Other preferred polyesters which can employ NDA monomer productin accordance with the present invention include any PTA/NDA polymerhaving molar ratios of PTA to NDA of 99:1 to 0:100. Preferred ranges ofNDA to PTA in NDA/PTA polyesters will range from 2 to 15 mole percentNDA to 98 to 85 mole percent PTA, with 2 to 9 mole percent NDA to 98 to91 mole percent PTA being more preferred. NDAs useful in the inventioncan be any polymerizable isomer such as 2,6-, 1,5-, 1,4- and 2,7-NDA, aswell as mixtures thereof. The polyesters also can include up to about 15mole percent of other carboxylic acids such as isophthalic acid and/oradipic acid. The polyester also may incorporate up to about ten molepercent of a glycol such as diethylene glycol, 1,4-butanediol,polybutadiene glycol or 1,4-cyclohexanedimethanol, or mixtures thereof.With respect to the ranges of process-related materials set forth inTable 1, above, it should be noted that higher levels of monomerimpurities are preferred in monomer product intended to be used as smallfractions of a copolymer, while lower levels of impurities will bepreferred where the monomer product comprises large fractions of acopolymer or where the end product is a homopolymer.

[0053] The inherent viscosity of polyesters in accordance with thepresent invention as measured in a 60/40 solution ofphenol/tetrachloroethane at 30° C. and a concentration of 0.4 grams/dLtypically will be between about 0.40 to 1.00 dL/gram, preferably about0.50-0.90 dL/g, and most preferably between about 0.60-0.80 dL/g.

[0054] The dicarboxylic acid component of polyesters in accordance withthe invention optionally may be modified with up to 15 mole percent ofone or more different dicarboxylic acids other than terephthalic acidand 2,6-naphthalenedicarboxylic acid. Such additional dicarboxylic acidsinclude aromatic dicarboxylic acids preferably having 8 to 14 carbonatoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbonatoms, or cycloaliphatic dicarboxylic acids preferably having 8 to 12carbon atoms. Examples of dicarboxylic acids to be included are phthalicacid, isophthalic acid, cyclohexanediacetic acid,4,4′-biphenyidicarboxylic acid, succinic acid, glutaric acid, adipicacid, fumaric acid, azelaic acid, sebacic acid,1,4-cyclohexanedicarboxylic acid, resorcinoldiacetic acid, diglycolicacid, 4,4-oxybis(benzoic) acid, 1,12-dodecanedicarboxylic acid,4,4′-sulfonyldibenzoic acid, 4,4′-methylenedibenzoic acid, trans4,4′stilbenedicarboxylic acid, 2,6-dicarboxytetralin,2,6-dicarboxydecalin, and the like.

[0055] Other additives and stabilizers known in the art such as glassfibers, mineral reinforcement, oxygen scavengers, diethylene glycolsuppressants, optical brightening agents and phosphorous-containingstabilizers can be incorporated into monomer product or polymers madetherefrom in accordance with the invention.

[0056] Monomers in accordance with the invention also may be used toproduce homopolymers and copolymers from relatively pure acids by addingthe materials described herein in the amounts set forth herein.

[0057] For example, metal salts particularly useful for preparingmetal-containing monomers include cobalt and manganese alkylates such asacetates, halides, especially bromides, and organic acid salts,particularly aromatic salts. When adding salts to relatively purearomatic acids, metal concentrations can range from about 20 to 10,000ppm by weight, more preferably between about 50 to 2000 ppm by weight,and most preferably between about 100-1000 ppm by weight.

[0058] If Co and Mn are added to produce a monomer in accordance withthe invention, the molar ratio of Co to Mn can range from 5:1 to 0.2:1,with the preferred ratios being between 4:1 to 0.25:1, and the mostpreferred ratios being between 3:1 and 0.5:1.

[0059] Polymers in accordance with the invention can be produced in thesame manner as polymers are produced from purer monomers of the sameacids. Such polymerization reactions are well-known in the art. See, forexample, The Encyclopedia of Chemical Technology, Vol. 18, pp. 531-594,John Wiley and Sons (1982), the disclosure of which is herebyincorporated by reference.

[0060] Co- and homopolyesters produced in accordance with the inventioncan be used to manufacture sheets and biaxially oriented films, fibers,stretch blow molded containers and any other application where suchpolyesters typically are employed. See, for example, PlasticsEngineering Handbook, 4th Edition, Van Nostrand Reinhold Company (1976),the disclosure of which is hereby incorporated by reference.

[0061] The presence of metals, color bodies and other impurities in theacid monomer of the present invention make these monomers particularlyuseful in NDA-copolymer applications where the presence of color isdesired or not objectionable, as well as where enhanced high temperatureperformance is required. Typical applications particularly suitable foruse of copolymers in accordance with the invention are containers forfood or beverages that require heating or pasteurization and which mustexhibit dimensional stability during and after the heating orpasteurization process. This is especially true where the packagedmaterial contains carbon dioxide or another gas which will generatesubstantial internal package pressure when heated. Specific examples ofsuch applications are pasteurizable bottles for beer, and bottles forfruit juices such as prune juice, where package heatability and colorare desired package characteristics. The utility of NDA/PTA copolymersis demonstrated by Example 7 below.

EXAMPLE 7

[0062] One half liter capacity, long neck, pasteurizable amber beerbottles having a champagne base were fabricated from experimentalcopolymers containing reslurried acid monomer in accordance with thecomposition described in Table 2, above.

[0063] In Example 7A, the PETN-3 copolymer employed contained 3 molepercent of the reslurried NDA and 97 mole percent of a purifiedterephthalic. In this Example, a 35.0 gram injection molding preform wasprepared. The preform contained approximately 15 grams of copolymer inthe shoulder area, about 10 grams of copolymer in the panel area, andabout 10 grams of material in the base area.

[0064] In Example 7B, a PETN-5 copolymer contained 5 mole percent of thereslurried NDA and 95 mole percent of the same purified terephthalicacid. In this Example, a 34.1 gram injection molding preform wasprepared. The preform contained approximately 14.7 grams of copolymer inthe shoulder area, about 10 grams of copolymer in the panel area, andabout 9.4 grams of material in the base area.

[0065] The preforms of Examples 7A and 7B were blown into 0.5 literbottles using a Sidel SBL2/3 stretch blow molding machine. Carbonatedwater containing about 2.9 to 3.1 volumes of carbon dioxide was added toeach bottle to a predetermined fill line and capped.

[0066] The capped bottles were placed in a pasteurization chamber andsprayed with 71 degree Centigrade water until the bottle contentsreached a temperature of about 63° C. The spray water temperature wasthen reduced to 64° C. to maintain the bottle contents at 63° C. for anadditional 15 minutes. Spray water temperature was then reduced untilthe bottle contents reached 40° C., after which time the bottles werechilled to room temperature in a cold water bath.

[0067] Several physical parameters of the pasteurized bottles weremeasured to determine the effects on the bottles from the pasteurizationprocess. The results of those measurements are summarized in Table 3below. TABLE 3 Bottle material PETN-3 PETN-5 Resin IV 0.80 0.80Dimensional Changes (% increase) Height 0.43 0.26 Diameter Upper Bumper1.94 2.15 Mid Panel 1.74 0.48 Lower Bumper 1.03 1.04 Neck 1.27 1.36 FillLine Drop (in.) 0.60 0.69 Perpendicularity (in. off 0.119 0.152 bottlecenter line) Pressure (volumes) 2.71 2.68

[0068] In the case of Examples 7A and 7B, both bottles′ dimensionalchanges were judged acceptable based on pressure retention (at least 75%of the prepasteurization pressure was retained when initially charged toa pressure of about 3 volumes), and perpendicularity (deviation from thevertical less than 0.25 inches for the vertical radial axis of bottlesymetry when the pasteurized bottle is standing on its base, with thedeviation measured at the top of the bottle. Fill line drops of lessthan 3 percent also are preferred.

[0069] It was also found that injection blow molding bottle preformscontaining between about 40-46 weight percent of their material in theshoulder region, 26-32 weight percent of their material in their panelregion and 25-31 weight percent of their material in the base regionwere most successful in withstanding the pasteurization tests. Theseapproximate preform weight distributions and geometries are believed tobe useful for half liter bottles formed from other polymers and arebelieved to be scalable for producing pasteurizable bottles of othervolumes.

[0070] While the foregoing examples describe the invention with respectto certain naphthalenic acid monomer products, those of ordinary skillin the art will recognize that the invention is equally useful inconnection with monomers such as terephthalic acid, isophthalic acid andthe like, with process-related materials present in approximately thesame ranges when corrected for the molecular weight difference betweennaphthalenic and other aromatic monomers. Additionally, when monomersaccording to the present invention are used to make copolymers, theprocess-related materials present in accordance with the presentinvention may be present, for example, in any one monomer, or in morethan one monomer. For these reasons, our invention is intended to belimited only by the scope of the following claims.

We claim:
 1. A process for producing a naphthalenic dicarboxylic acidmonomer product suitable for the manufacture of polyesters, said processcomprising the steps of: oxidizing a naphthalenic feedstock to produce acrude naphthalenic dicarboxylic acid; processing the crude naphthalenicdicarboxylic acid to produce a naphthalenic dicarboxylic acid monomerproduct comprising at least 90 mole percent of the acid monomer and oneor more process-related materials selected from the group consisting ofbetween 50 and 5,000 ppm of monofunctional materials, between 50 and10,000 ppm of trifunctional materials, between 50 and 500 ppm of colorbodies, and between 50 and 10,000 ppm of metals.
 2. The process of claim1 further comprising the step of polymerizing the naphthalenicdicarboxylic acid monomer product of claim 1 into a homopolymer or acopolymer without performing an intervening process step intended toremove the process-related materials from the monomer product prior toconducting the polymerization step.
 3. The process of claim 2 whereinthe processing step includes slurrying the crude naphthalenicdicarboxylic acid in a solvent selected from the group consisting ofwater, aliphatic organic acids having between 2 and 4 carbon atoms, andmixtures thereof.
 4. The process of claim 1 wherein the mole percent ofa naphthalenic compound which is to be oxidized to form a desirednaphthalenic dicarboxylic acid monomer comprises at least 95 molepercent of the naphthalenic material in the feedstock.
 5. The process ofclaim 3 wherein the slurrying step is performed at a temperature ofabout 60 to 125° C., at a pressure of from about 0.5 to 3 atmospheres,and at a solvent to crude naphthalenic acid weight ratio of about 0.5:1to 20:1.
 6. The process of claim 3 wherein the slurrying step isperformed at a temperature of about 75 to 110° C., at a pressure of fromabout 1 to 2 atmospheres, wherein the solvent comprises at least 50 molepercent acetic acid, and at a solvent to crude naphthalenic acid weightratio of about 1:1 to 10:1.
 7. The process of claim 1 wherein theprocess-related materials are selected from the group consisting ofbetween 150 and 3,500 ppm of monofunctional materials, between 150 and8500 ppm of trifunctional materials, between 50 and 250 ppm of colorbodies, and between 500 and 2,000 ppm of metals, and combinationsthereof.
 8. The process of claim 1 wherein the process-related materialincludes from between 150 and 3,500 mole percent of monofunctionalmaterials.
 9. The process of claim 1 wherein the process relatedmaterial includes from between 150 and 8,500 mole percent oftrifunctional materials.
 10. The process of claim 1 wherein the processrelated material includes from between 50 and 250 mole percent of colorbodies.
 11. The process of claim 1 wherein the process-related materialincludes from between 500 and 2,000 mole percent of metals selected fromthe group consisting of cobalt, manganese, and mixtures thereof.
 12. Theprocess of claim 2 further comprising the step of producing ahomopolymer or copolymer article from the polymerized naphthalenicdicarboxylic acid monomer product, said article being selected from thegroup consisting of sheets, films, oriented films, fibers, injectionmolded articles, and blow molded articles.
 13. The process of claim 2wherein the copolymer is formed from between about 2 and 15 mole percentof the polymerized naphthalenic dicarboxylic acid monomer product andfrom between about 98 and 85 mole percent of one or more aromatic acidsselected from the group consisting of terephthalic acid, isophthalicacid, and adipic acid, and mixtures thereof.
 14. The process of claim 2wherein the copolymer is formed from monomer comprising between about 2and 9 mole percent of the naphthalenic dicarboxylic acid monomer productand from between about 91 and 98 mole percent of terephthalic acid. 15.The naphthalenic dicarboxylic acid monomer product produced by theprocess of claim
 1. 16. The product of claim 15 comprising between about50 and 250 ppm of color bodies and exhibiting a tristimulus color valueof greater than 0 on a yellow/blue scale.
 17. A polyester comprising atleast 2 mole percent of the product of claim 16 having a tristimuluscolor value of greater than +10 on a yellow/blue scale.
 18. Anaphthalenic dicarboxylic acid monomer product suitable for themanufacture of polyesters, said product comprising at least 90 molepercent of the acid monomer and one or more materials selected from thegroup consisting of between 50 and 5,000 ppm of monofunctionalmaterials, between 50 and 10,000 ppm of trifunctional materials, between50 and 500 ppm of color bodies, and between 50 and 10,000 ppm of metals,and combinations thereof.
 19. The composition of claim 18 wherein one ormore of the one or more materials is a process-related materialresulting from manufacture of the product.
 20. The composition of claim19 wherein the process-related material is selected from the groupconsisting of between 150 and 3,500 ppm of monofunctional materials,between 150 and 8,500 ppm of trifunctional materials, between 50 and 250ppm of color bodies, and between 500 and 2,000 ppm of metals selectedfrom the group consisting of cobalt and manganese, and combinationsthereof.
 21. The product of claim 19 comprising between about 50 and 250ppm of color bodies and exhibiting a tristimulus color value of greaterthan 0 on a yellow/blue scale.
 22. A polyester comprising at least 2mole percent of the product of claim 21 and having a tristimulus colorvalue of greater than +10 on a yellow/blue scale.
 23. A copolymer formedfrom monomer comprising between about 2 and 10 mole percent of thepolymerized naphthalenic dicarboxylic acid monomer product of claim 18and from between about 98 and 91 mole percent of terephthalic acid. 24.An article formed from the copolymer of claim 23, said article beingselected from the group consisting of sheets, films, oriented films,fibers, injection molded articles, and blow molded articles.
 25. Aprocess for producing a naphthalenic dicarboxylic acid monomer product,said process comprising the steps of: oxidizing a naphthalenic feedstockto produce a crude napthalenic dicarboxylic acid comprising anaphthalenic dicarboxylic acid useful as a monomer in a polymerizationreaction and process-related materials formed during the manufacture ofthe crude naphthalenic dicarboxylic acid; slurrying the crudenaphthalenic dicarboxylic acid in a solvent to remove a portion ofprocess-related materials from the crude naphthalenic dicarboxylic acid;recovering solid monomer from the slurry to produce a naphthalenicdicarboxylic acid monomer product comprising at least 93 mole percent ofthe acid monomer and one or more process-related materials selected fromthe group consisting of between 50 and 5,000 ppm of monofunctionalmaterials, between 50 and 10,000 ppm of trifunctional materials, between50 and 500 ppm of color bodies, and between 50 and 10,000 ppm of metals.26. The process of claim 25 wherein a recrystallization step is notperformed between the oxidizing step and the recovering step.
 27. Theprocess of claim 25 further comprising polymerizing the naphthalenicdicarboxylic acid monomer product into a homopolymer or a copolymerwithout first performing an intervening process step intended to removethe process-related materials from the monomer product prior toconducting the polymerization.
 28. The process of claim 25 wherein thecrude naphthalenic dicarboxylic acid is slurried in a solvent selectedfrom the group consisting of water, aliphatic organic acids havingbetween 2 and 4 carbon atoms, and mixtures thereof.
 29. The process ofclaim 26 wherein the process-related materials are selected from thegroup consisting of between 150 and 3,500 ppm of monofunctionalmaterials, between 150 and 8,500 ppm of trifunctional materials, between50 and 250 ppm of color bodies, and between 500 and 2,000 ppm of metals.30. The process of claim 27 wherein the copolymer is formed from monomercomprising between about 2 and 9 mole percent of the polymerizednaphthalenic dicarboxylic acid monomer product and from between about 98and 91 mole percent of terephthalic acid.
 31. The process of forming,from the copolymer of claim 30, an article selected from the groupconsisting of sheets, films, oriented films, fibers, injection moldedarticles, and blow molded articles.
 32. A pasteurizable blow-moldedbottle prepared from a polymerized material comprising a copolymerformed by the process of claim 30, wherein the copolymer containsbetween about 2 and 9 mole percent of the naphthalenic dicarboxylic acidmonomer product and from between about 98 and 90 mole percent ofterephthalic acid, said bottle being capable of containing agas-containing liquid during a pasteurization process in which thetemperature of the gas-containing liquid is maintained at a temperatureof at least 60° C. for at least 15 minutes during said process, andwherein said bottle is capable of retaining at least 70 percent of aninitial gas pressure when charged to an initial gas pressure of about 3volumes of gas per bottle volume.
 33. The bottle of claim 32 wherein,after pasteurization, the bottle has a vertical axis of radial symetrythrough the bottle which deviates from perpendicular of less than 0.25inches.
 34. The bottle of claim 32 wherein the bottle is a bottle havingan approximate 500 milliliter capacity, and wherein the bottle is blownfrom a preform having a shoulder area, a panel area and a base area,said areas expanding during the blowing process under exposure to heatand pressure to form a blow molded bottle, and in which the shoulderarea contains between about 14 to 16 grams of polymer, wherein the panelarea contains between about 9 to 11 grams of polymer, and wherein thethe base contains between about 8.5 and 11 grams of polymer.